A wire harness is routed through a through-hole in a body panel that partitions an area exposed to water and a passenger cabin in a vehicle. A grommet composed of rubber or elastomer is mounted on the wire harness and is engaged with an inner periphery of the through-hole to shield the passenger cabin from water.
In many cases, a larger through-hole in the body panel to which the grommet is attached is provided with a burring hole having a burring B that projects to one side from a periphery of a through-hole H, as shown in FIG. 6(A).
In a case where the through-hole H in a body panel P is such a burring hole, a grommet 100 to be inserted and engaged with the through-hole H has an annular body engagement recess 112 and a seal lip 113, as shown in FIGS. 6(A) and (B), the body engagement recess 112 being provided in an outer periphery of a large diameter side of a diameter-increasing tubular portion 111 that extends from a small-diameter tubular portion 110 through which a wire harness 101 is tightly attached and inserted, the seal lip 113 being provided in a bottom surface 112a of the body engagement recess 112. The bottom surface 112a of the body engagement recess 112 is interposed between a side wall 112b of an inclined wall 115 and a side wall 112c of a front end thick portion 116.
To attach the grommet 100 to the through-hole H, the small-diameter tubular portion 110 of the grommet 100 is inserted through the through-hole H of the body panel P; the inclined wall 115 that defines the bottom wall 112a of the body engagement recess 112 is compressed and deformed to set a burring B of the through-hole H into the body engagement recess 112; and the seal lip 113 is pressed against an inner peripheral surface of the burring B. A point where the seal lip 113 is pressed against the burring B is referred to as a seal point SP.
With the burring B projecting from the periphery of this type of through-hole H, the height (projection amount) of the burring varies, and so does the radius from the periphery of the through-hole H. Thus, it is necessary to design a grommet in consideration of differences and variations of the height of the burring, the curvature of the radius, and the inner diameter of the through-hole.
In addition, a radius portion Br of the burring B rides on the seal lip 113, as shown in FIG. 6(C), making it difficult to control required seal pressure. Furthermore, due to a difficulty in securing a large overlap amount in consideration of a variation in the projection amount of the burring B, the seal lip 113 is relatively large. Thus, an “engagement amount A” of the grommet 100 to the burring B is insufficient, likely to lead to an insufficient gripping force. With a large “engagement amount A” and a large projection amount of the inclined wall 115, however, an insertion force to insert the grommet 100 into the through-hole H is increased.
A conventional grommet to be attached to a through-hole H having a burring B is disclosed in Japanese Patent Laid-Open Publication No. H9-63385. With reference to FIGS. 7(A) and (B), the grommet 200 is a two-piece component that includes an outer member 201 composed of an elastic material, such as rubber, and an inner member 202 composed of a resin molded component. A projecting end surface Ba of the burring B projecting from the periphery of the through-hole H is pressed against a hole end contact portion 201 a of the outer member 201, and a lip pressing portion 202a of the inner member 202 is inserted into the hole end contact portion 201 a of the outer member 201. In addition, the burring B is pressed by the inner member 202 from the periphery of the through-hole, and is thus held between the outer member 201 and the inner member 202 to maintain sealing performance.